Completed - task moves to this state when it successfully completes its work.

Failed - task moves to this state when it fails completes its work.

Pending - initial state, every task started as Pending.

Running - task moves to this state when worker successfully starts the task.

Scheduled - task moves to this state, once manager has scheduled it onto worker.

Docker - encapsulate interaction with docker SDK.

DockerResult - result for start/stop container operations.

Task - orchestrator task description.

TaskEvent - event that used by task system for state transition.